Conventional athletic or running shoes generally have at least three components. An outsole is usually fabricated of a fairly tough and only slightly cushionable material such as rubber. A midsole of more cushionable material is conventionally glued on top of the outsole, and an upper is attached on top of the midsole.
Conventionally, the midsole element in running or athletic shoes has been made of a single type of material. Some manufacturers have used ethylene vinyl acetate (EVA). Other manufacturers have used a midsole of polyurethane. Tests have proven that a midsole formed totally of EVA provides good cushioning, but is not sufficiently hard or resilient to provide proper support for the foot. On the other hand, midsoles made entirely of polyurethane are hard and unyielding with little cushioning provided.
Therefore, a need exists to provide a midsole which furnishes the wearer both proper support and provides him or her with an appropriate amount of cushioning.